The present invention involves reactors for dehydoxylation and alkylation of porous silicate films, as for example, mesoporous silica films on wafers or substrates. More particularly, it concerns vacuum/gas phase reactors capable of producing films exhibiting low dielectric constant (low-k) and high elastic modulus (high-E) films at relatively low temperatures that are compatible with manufacture of semiconductor interconnects.
The reaction involves the capping of polar hydroxyl groups on the surfaces of the porous silicates, which include silica and organosilicates with alkyl or alkyl silane groups resulting in a non-polar hydrophobic surface. Liquid/solution phase treatment involves dipping or soaking the substrate (typically supported on silicon wafers) in pure silane or a silane solution followed by a solution wash. Gas phase treatment is generally more efficient and involves treating the substrate with a silane or other dehydroxylating organic chemicals in the gas phase at elevated temperatures and/or reduced pressures. The substrate is exposed to vacuum prior to and after silane treatment. Such gas phase treatment is described in the above-referenced co-pending U.S. patent application Ser. No. 09/413,062 entitled MESOPOROUS SILICA FILM FROM A SOLUTION CONTAINING A SURFACTANT AND METHODS OF MAKING SAME, filed Oct. 4, 1999 and assigned in common with the present application to Battelle Memorial Institute, Inc. of Richland, Wash., the disclosure of which is incorporated herein by this reference. The greater efficiency of vacuum/gas phase silane or dehydroxylating chemical treatment (hereinafter termed xe2x80x9csilylationxe2x80x9d) can be attributed to the greater accessibility of silane or other dehydroxylating chemicals to the hydroxyl moieties after pore evacuation, especially with pore sizes in the ten to twenty angstrom (10-20 xc3x85) range.
Ideally, the reactor used in gas phase silylation reactions would be one in which the substrate could be subjected to high vacuum, heated to target temperature, and treated with silane as quickly and efficiently as possible.
Various reactor designs can accomplish this treatment of films. However, the specific design employed can affect the quality of the final product. To better facilitate the silylation and to increase the efficiency of the process, the reactor is designed to contain quasi-catalytic surfaces which can act both as an xe2x80x9cactivatorxe2x80x9d to put species in a higher energy state or a highly activated state, and as a xe2x80x9cscrubberxe2x80x9d to eliminate possible poisons or reactive by-products generated in the silylation reactions. One described embodiment is a hot filament reactor having hot, preferably metallic-solid surfaces within the reactor""s chamber in which mesoporous film wafers are placed. Another is an IR reactor having upper and lower quartz windows sealing the upper and lower periphery of an aluminum annulus to form a heated chamber. Finally, a flange reactor is described that includes a flange base and lid forming a tiny chamber therein for a wafer, the reactor being heated by conduction from a hot sand bath. The silylation treatment of mesoporous films produces treated films exhibiting low dielectric constant (k) and high modulus (E).
The subject matter of the present invention is particularly pointed out and distinctly claimed in the concluding portion of this specification. However, both the organization and method of operation, together with further advantages and objects thereof, may best be understood by reference to the following description taken in connection with accompanying drawings wherein like reference characters refer to like elements.